To provide a high-strength hot-rolled steel sheet that has both excellent strength and excellent workability (especially, stretch flange formability), and to provide a manufacturing method therefor.
The high-strength hot-rolled steel sheet whose tensile strength is 850-1,150 MPa and which is excellent in workability has a composition containing, by mass, 0.05-0.09% C, 0.3% or less Si, 1.00% or less Mn, 0.03% or less P, 0.007% or less S, 0.1% or less Al, 0.01% or less N, and 0.18-0.25% Ti so as to satisfy a relation: 1.0≤([C]/12)/([Ti*]/48)≤1.5 (wherein [C], [N] and [Ti] are contents of the respective elements contained (mass%), and [Ti*]=[Ti]-3.4×[N]) with the remainder comprising Fe and unavoidable impurities, and has a structure in which an area rate of a ferrite phase is 95% or more, an average crystal grain size of the ferrite phase is 10 μm or less, and an average particle size of carbide in the crystal grain of the ferrite phase is less than 10 nm.
FUNAKAWA YOSHIMASA
SHIGEMI MASAHITO
OKUBO HIDEKAZU
KANEMURA TOKUNORI
| JP2010053434A | 2010-03-11 | |||
| JP2007302992A | 2007-11-22 | |||
| JP2007291519A | 2007-11-08 | |||
| JP2009024226A | 2009-02-05 | |||
| JP2004225109A | 2004-08-12 | |||
| JP2013124395A | 2013-06-24 |
Suzuki Yoko
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